A spin-valve magnetoresistive sensor using a multi-layered antiparallel pining layer and an antiferromagnetic exchange layer are disclosed in JP-A No.16929/1997. A spin-valve sensor using an antiferromagnetic coupling film is disclosed in JP-A-169026/1995. A magnetoresistive element having a second magnetic layer including a third layer made from any of materials such as oxides, on which magnetization is substantially fixed, is disclosed in JP-A-156530/2000.
The Abstracts of 23th Academic Lectures, 6aA-5 published by the Magnetics Society of Japan describes the spin valve film having a magnetization pinned layer including an ultra thin oxide layer. Digest of Intermag 2000, FA-08 describes a giant magnetoresistive (GMR) film using also a thin oxide layer. Digest of Intermag 2000, FA-07 describes the GMR film with a protective oxide film deposited on a free layer. Digest of Intermag 2000, BQ-12 describes the GMR film with a protective oxide film deposited on a free layer. Digest of Intermag 2000, FA-09 describes the spin valve film using the magnetic oxide layer. Digests of Intermag 1999, DB-01 describes the spin valve film using the pinned layer with the oxide layer inserted.
The magnetoresistive type of head, which uses a high spin-polarized oxide material in the magnetic layer to supply current perpendicular to the surface of the film is disclosed in JP-A-340859/2000. A tunnel magnetoresistive element using a high-polarized film is disclosed in JP-A-150985/2000. A magnetoresistive element using a high-polarized film on a tunnel barrier layer side is disclosed in Patent No. 3050189 (JP-A-135857/1999). A spin-polarized element, to which a ferromagnetic material and semiconductor or a half-metalic material are connected through a non-magnetic layer is disclosed in JP-A-289115/1999.
The descriptions of a ferromagnetic tunnel magnetoresistive element using LaSrMnO3 as a half-metalic material are found in Applied Physics Letters, vol. 73, 1008 (1998). Applied Physics Letters, vol. 74, 4017 (1999) describes ferromagnetic tunnel magnetoresistance achieved by means of materials, iron oxide and Co.
The ferromagnetic tunnel magnetoresistive element using a half-metalic oxide layer is disclosed in JP-A-97766/1999. A magnetoresistive device using a half-metalic material such as Fe3O4 is disclosed in JP-C-504303/1996. The magnetoresistive element using the magnetic layer made from the half-metalic material is disclosed in JP-A-267742/1994. A spin valve sensor including thin oxide layers is disclosed in JA-348935/2000.
In the related art, it is impossible to successfully dispose the magnetoresistive element, which acts on an external magnetic field with sufficient sensitivity and output power and provides good characteristics with a well symmetric property, at the reproducing part of a magnetic recording device, which makes it different to implement the function indispensable to the device with a considerably high level of recording density.
A giant magnetoresistance, which is achieved by means of a multi-layered film with ferromagnetic metal layers deposited through a non-magnetic metal layer, is well known to those skilled in the art. With respect to this type of magnetoresistance, electrical resistance varies with both of magnetization formed on the ferromagnetic layer isolated by the non-magnetic layer and an orientation of the magnetization. A spin-valve structure is proposed so that said giant magnetoresistance may be applied to the magnetoresistive element. This means that the preferred output power can be supplied by achieving the structure of an antiferromagnetic film/an ferromagnetic metal layer/a non-magnetic metal layer/a soft-magnetic metal layer and by substantially fixing the magnetization of the ferromagnetic metal layer stuck fast to the antiferromagnetic film by means of an exchange coupling field induced on an interface between the antiferromagnetic film and the ferromagnetic metal layer to magnetically rotate the counterpart, that is, the soft magnetic metal layer.
Hereafter, in the following descriptions, the above-mentioned effect of magnetization fixation is simply referred to as pinned bias and the antiferromagnetic film, as a pinned bias film. In addition, the ferromagnetic metal layer, on which the above-mentioned magnetization is substantially fixed, is simply referred to as a pinned film or ferromagnetic pinned layer. Similarly, the soft magnetic metal film, which is magnetically rotated by means of the external magnetic field, is simply referred to as a free layer or soft magnetic free layer.
The pinned layer provides such a function that it has the magnetization substantially fixed so that the magnetic field may be sensed and the antiferromagnetic film may be alternatively replaced with a hard magnetic film, that is, another material, which does not affect the magnetization unless a relatively strong magnetic field is applied.
In the magnetic head using the spin valve type of magnetoresistive multi-layered film, the part composed of the ferromagnetic layer/the non-magnetic layer/the soft magnetic layer determines the magnitude of its magnetoresistance. Since the soft magnetic metal layer is one kind of ferromagnetic metal layer, the ferromagnetic metal layer-non-magnetic metal layer interface is responsible for the principle. It is known that the public known art allows improvement in MR ratio by inserting an oxide into the ferromagnetic metal layer or by oxidizing part of it. In this case, however, the oxide layer is deposited at a midpoint of the ferromagnetic metal layer but a given thickness of oxide layer is not disposed at the ferromagnetic metal layer-non-magnetic metal layer interface. That is because the oxide has generally no ferromagnetic property and dose not transmit electrons, which is a major blocking factor of magnetoresistance.
Alternatively, the method for increasing magnetoresistance by applying a material of high-polarization has been also proposed but it is very difficult to laminate thin metal films such as ferromagnetic metal layers and the compounds such as the high-polarized oxide for fabricating the magnetoresistive element. This is due to the problems that alternately laminating the high-polarized material usually composed of compounds such as oxides with metal layers may cause the high-polarized material to react to the metal layers, or may cause constituents of the material to diffuse in the metal layers to form a non-stoichiometric composition, resulting in deterioration in properties.
Further, when the thin films are laminated using the conventional film formation technique, such a problem is encountered that an amorphous or microcrystal structure or a heterogeneous crystal structure is formed. As an example, in case of magnetite (Fe3O4), which is known for a half-metalic material, the thin film formed by the sputtering method at room temperature using the target of magnetite exhibits a magnetization property of only a level ranging from one third to a half of 0.6 tesla for bulk magnetite. To achieve a good thin crystalline magnetite film, the temperature of a substrate needs to be turned up to approx. 500° C. Film formation, however, at such a higher temperature of the substrate not only makes it difficult to continuously form other metal layers and disturbs formation of ultra thin flattened metal layers, but also significantly accelerate the reactions between the high-polarized layers and other metal layers, for example, CoFe layers, interfering with formation of preferable high-polarized layers. Thus, it is practically very difficult to laminate the magnetoresistive film with high-polarized layers and metal layers deposited.